I identified the surges of warm air problem as operator error.
I didn't realize that chassis heater rocker switch was in Low instead of Off. Plus I didn't realize the chassis heater puts hot air out through the coach heating vents. I thought they were completely separate systems.
In addition, my right foot is getting quite a bit of heat off the side of the doghouse so I need to do some insulating.
I still haven't tracked down what's causing the Max A/C to not cool as much as regular A/C since I tried it after correcting the above but it's probably a venting issue.
I'm also not sure the valve that controls the water flow to the heater core is shutting off completely -- another thing for my list. I see where some have replaced it with a manual ball valve. It would be just like me to do so, forget to turn it back on this winter and be posting that I'm not getting any heat.